An ink supply device includes an ink container (3; 20; 60; 90) connected to an air communication port (31; 80) through a porous member (33; 43; 52; 62; 92). The ink container (3; 20; 60; 90) is maintained at a negative pressure equivalent to the capillary force of the ink penetrated into the porous member (33; 43; 44; 52; 62; 92). Since the ink container is in communication with the air through a wide area of the porous member (33; 43; 52; 62; 92), the ink container (3; 20; 60; 90) can be maintained at a constant negative pressure regardless of the quantity of ink consumed by the recording head.